Beyond the 10%: Unraveling the genetic diversity in Turkish cystic fibrosis patients not eligible for CFTR modulators.

ABSTRACT

BACKGROUND: Cystic fibrosis (CF) is an autosomal recessive disease caused by variants of CFTR gene. Over 2000 variants have been identified, and new drugs called CFTR modulators have been developed to target specific defects in the CFTR protein. However, these drugs are only suitable for patients with certain variants of CFTR, and eligibility rates vary depending on race and geographical region. This study aimed to reveal the detailed genotype and clinical characteristics of people with CF (pwCF) at our center in Turkey, a developing country, who are not eligible for CFTR modulators. METHODS: A total of 445 pwCF followed up at Marmara University were reviewed retrospectively. Variants of the patients ineligible to CFTR modulators were classified based on American College of Medical Genetics guidelines, CFTR classification, the change in the encoded protein, and the variant type. RESULTS: The study revealed that 139 (31.2%) patients weren't eligible for CFTR modulators. There were 60 different variants in the 276 alleles, as two were missing. The majority of patients had missense or nonsense variants, and that the most common variant was c.1545_1546del, which can be said unique to this geography. CONCLUSION: The study highlights the importance of detecting the variants of ineligible patients in detail to guide future approaches for more targeted and effective interventions in CF care. Testing the effectiveness of CFTR modulators for rare or newly occurring variants is crucial to ensure equal access for pwCF to these therapies from different racial backgrounds and ethnic minorities.